ACTIVATOR HAVING A LOW PH VALUE FOR SUPPLEMENTARY CEMENTITIOUS MATERIAL

Abstract

Activators for supplementary cementitious material, comprising reactive belite, obtainable by hydrothermal treatment of a starting material, which contains sources for CaO and SiO2 in an autoclave at a temperature of 100 to 300 C. and tempering the obtained intermediate product at 350 to 495 C., hydraulic binders based on the supplementary cementitious material above, and by a method for activating the supplementary cementitious material by adding reactive belite obtainable by hydrothermal treatment of a starting material which contains sources for CaO and SiO.sub.2 in an autoclave at a temperature of 100 to 300 C. and tempering the obtained intermediate product at 350 to 495 C. and the use of the reactive belite containing material as activator.

Claims

1-19. (canceled)

20. An activator for supplementary cementitious material that comprises reactive belite, containing x-Ca.sub.2SiO.sub.4 in an amount of >30% by weight and at least one X-ray amorphous phase in an amount of >5% by weight, and is obtainable by hydrothermal treatment of a starting material, which contains sources for CaO and SiO.sub.2, in an autoclave at a temperature of 100 to 300 C. and a residence time of 0.1 to 24 hours, and tempering the obtained intermediate product at 350 to 495 C. and a residence time of 0.01 to 600 min.

21. A hydraulic binder based on supplementary cementitious material and reactive belite, containing x-Ca.sub.2SiO.sub.4 in an amount of >30% by weight and at least one X-ray amorphous phase in an amount of >5% by weight, as an activator, wherein the activator is obtainable by hydrothermal treatment of a starting material, which contains sources for CaO and SiO.sub.2, in an autoclave at a temperature of 100 to 300 C. and a residence time of 0.1 to 24 hours, and tempering the obtained intermediate product at 350 to 495 C. and a residence time of 0.01 to 600 min.

22. The binder according to claim 21, wherein it contains 5 to 95% by weight supplementary cementitious material and 5 to 95% by weight activator, preferably 30 to 85% by weight supplementary cementitious material and 15 to 70% by weight activator, particularly preferred 40 to 80% by weight cementitious and 20 to 60% by weight activator, wherein the values are based on the total amount of binder and the proportions add up to 100% with the rest of the binder components.

23. The binder according to claim 21, wherein the supplementary cementitious material is selected from tempered clays, such as metakaolin and shale; V and W fly ash having a high glass content and/or a content of reactive phases; ground granulated blast furnace slags; artificial (pozzolanic and latent-hydraulic) glasses and mixtures thereof.

24. The binder according to claim 21, further comprising admixtures and/or additives.

25. The binder according to claim 24, further comprising additives selected from hydraulically non-active components, such as ground limestone/dolomite, precipitated CaCO.sub.3, Mg(OH).sub.2, Ca(OH).sub.2, CaO, silica fumes and glass flour.

26. The binder according to claim 24, wherein, in total, the binder contains additives in an amount ranging from 1 to 25% by weight, preferably from 3 to 20% by weight and yet more preferably from 6 to 15% by weight.

27. The binder according to claim 24, the admixtures are selected from setting accelerators, hardening accelerators, concrete water reducing agents, plasticizers, retarders and mixtures thereof.

28. The binder according to claim 21, further comprising at least one additional hydraulic material, preferably Portland cement.

29. The binder according to claim 28, wherein the additional hydraulic material is present in an amount of from 1 to 70% by weight, in particular from 5 to 40% by weight and particularly preferred from 10 to 25% by weight.

30. A method for activating latent-hydraulic and/or pozzolanic materials by adding reactive belite, containing x-Ca.sub.2SiO.sub.4 in an amount of >30% by weight and at least one X-ray amorphous phase in an amount of >5% by weight, that is obtainable by hydrothermal treatment of a starting material, which contains sources for CaO and SiO.sub.2, in an autoclave at a temperature of 100 to 300 C. and a residence time of 0.1 to 24 hours, and tempering the obtained intermediate product at 350 to 495 C. and a residence time of 0.01 to 600 min to form a reactive belite containing activator.

31. The method according to claim 30, wherein the activator is ground together with the supplementary cementitious material.

32. The method for producing a binder according to claim 21, containing supplementary cementitious material and an activator, containing x-Ca.sub.2SiO.sub.4 in an amount of >30% by weight and at least one X-ray amorphous phase in an amount of >5% by weight, wherein the activator is obtained by hydrothermal treatment of a starting material, which includes sources for CaO and SiO.sub.2, in an autoclave at a temperature of 100 to 300 C. and tempering the obtained intermediate product at 350 to 495 C., wherein the intermediate product is ground together with the supplementary cementitious material or a part thereof.

33. A building material, in particular concrete, mortar, plaster, screed or sealant, containing the binder according to claim 21, and at least one of aggregates, admixtures and additives.

34. Use of reactive belite, containing x-Ca.sub.2SiO.sub.4 in an amount of >30% by weight and at least one X-ray amorphous phase in an amount of >5% by weight, obtainable by hydrothermal treatment of a starting material, which contains sources for CaO and SiO.sub.2, in an autoclave at a temperature of 100 to 300 C. and a residence time of 0.1 to 24 hours, and tempering the obtained intermediate product at 350 to 495 C. and a residence time of 0.01 to 600 min to form an activator containing reactive belite, as an activator of latent-hydraulic and/or pozzolanic supplementary cementitious material in hydraulic binders.

35. The use according to claim 34, wherein from 5 to 95% by weight supplementary cementitious material and 5 to 95% activator, preferably 30 to 85% by weight supplementary cementitious material and 15 to 70% by weight activator, particularly preferred 40 to 80% by weight supplementary cementitious material and 20 to 60% by weight activator, wherein the values are based on the total amount of binder and the proportions add up to 100% with the rest of the binder components.

Description

EXAMPLES

[0067] In table 2, the ground granulated blast furnace slag (HS) used, with which the examples described below have been carried out, is characterised by means of its oxidic main components. The weight loss after tempering at 1000 C is also stated. The grinding fineness is 5750 cm.sup.2/g according to Blaine.

TABLE-US-00002 TABLE 2 Component Content [%] LOI 1000 C. 0.5 SiO.sub.2 35.4 Al.sub.2O.sub.3 12.6 TiO.sub.2 1.18 MnO 0.28 Fe.sub.2O.sub.3 0.4 CaO 42.9 MgO 4.8 K.sub.2O 0.36 Na.sub.2O 0.24 SO.sub.3 0.2 P.sub.2O.sub.5 0.04 S 1.35 Total 100.15

Example 1

[0068] Firstly, an intermediate product is synthesised as follows for the production of the reactive belite as the activator. Producing a mixture of Ca(OH).sub.2 and nano-SiO.sub.2 in a molar ratio of 2:1. After adding seed crystals from 5% by weight -2CaO.SiO.sub.2.H.sub.2O, the mixture was homogenised with water. The ratio of water/solid was 2. An autoclave treatment at 15 bar for 16 h followed. Subsequently, drying at 60 C. took place. The intermediate product was composed of 97% by weight of -2CaO.SiO.sub.2.H.sub.2O and 3% by weight of amorphous components. By subsequently tempering at 420 C., the intermediate product was transformed into the activator containing reactive belite. The activator consisted of 50% by weight of X-ray amorphous material, 40% by weight of x-Ca.sub.2SiO.sub.4, 5% by weight of -Ca.sub.2SiO.sub.4 and 3% by weight of -2CaO.SiO.sub.2.H.sub.2O and 2% by weight of calcite. The activator produced in such a way was then mixed with 20 and 80% by weight of ground granulated blast furnace slag and homogenised in a tumble mixer. The two mixtures and the pure ground granulated blast furnace slag and the pure activator comprising reactive belite were tested by means of heat flow calorimetry for hydraulic reactivity. FIG. 1 shows the heat flow rates measured and the cumulative heat release. Table 3 compares the expected amounts of heat, which were calculated from the proportions of the pure components, with the amounts of heat measured of the mixtures.

TABLE-US-00003 TABLE 3 Activator Granulated slag Total reaction heat after 3 Total heat Total heat days Proportion contribution* Proportion contribution* Calculated sum* Measurement [Mass %] [J/g] [Mass %] [J/g] [J/g] [J/g] 100 246 0 0 246 246 80 197 20 6 203 248 20 49 80 32 81 183 0 0 100 40 40 40 *calculated for the mixtures from the proportion of the component.

[0069] The comparison shows that the amounts of heat measured are clearly higher than those calculated from the components. The difference can be traced back to an activation of the granulated slag. The hydration products of the mixture of activator containing reactive belite and 20% by weight of granulated slag were also tested by means of scanning electron microscopy. FIG. 2 shows that hydration products of the ground granulated blast furnace slag were formed.

Example 2

[0070] A mixture of Ca(OH).sub.2 and highly dispersed SiO.sub.2 was produced in a molar ratio of 2:1. After the addition of seed crystals from 5% by weight of -2CaO.SiO.sub.2.H.sub.2O, the mixture was homogenised with water. The ratio of water/solid was 10. An autoclave treatment followed with constant stirring at 200 C. for 16 h. Subsequently, a drying at 60 C. took place. The intermediate product contained 87% by weight of -2CaO.SiO.sub.2.H.sub.2O, 2% by weight of calcite, 2% by weight of scawtite and 9% by weight of amorphous components. The dried intermediate product was mixed with 40% by weight of ground granulated blast furnace slag and ground in a planetary ball mill for 3 min. Subsequently, a tempering at 420 C. took place. The measuring of the heat development by means of heat flow calorimetry is depicted in FIG. 3. The binder was tested in terms of compressive strength development. The water/binder ratio (w/b) was set to 0.3 by plasticizers. The strength was checked on cubes with an edge length of 4 cm. Strengths of 62 N/mm.sup.2 emerged after 2 days, 77 N/mm.sup.2 after 7 days and 85 N/mm.sup.2 after 28 days.

Example 3

[0071] The pH value of calcium hydroxide, OPC and activator according to the invention was measured after mixing with water. The results are depicted in FIG. 4. Calcium hydroxide, light grey curve CH, had a pH value of 12.6 practically immediately after mixing. Portland cement, dotted curve OPC, also quickly obtained a pH value above 12. The activator according to the invention, black curve CSH, in comparison to OPC, shows a quicker solution, wherein the pH value, though, remained below 12.5 for more than 30 minutes and was also still below 12.6 after 1 hour. Thus, the activator according to the invention has a lower pH value than OPC or calcium hydroxide and a much lower pH value than sodium or potassium hydroxide.